Seismic, morphologic and scale variabilities of subsurface pipes and vent complexes in a magma-rich margin

Subsurface pipes related to fluid flow are observed in seismic reflection data as vertical to sub-vertical features of low-amplitude reflections, linking chaotic reflections at the base (root zones) of volcanic constructs to their summits which can comprise craters, mounds or eye-shaped vents. To date, uncertainties remain regarding the linear correlation and scaling relationship between pipes and their overlying vent structures. Using 3D seismic reflection data from a magma-rich basin, the Vigrid Syncline in the Vøring Basin (offshore Norway), this study provides a seismic, morphometric and statistical description of forty (40) pipes and their associated structures. These pipes include conical, bifurcated, fault-controlled and columnar types, which are a consequence of the intrusion of two mappable magmatic sills of Early Eocene age. The heights (av. 1098 m), widths (av. 1740 m) and slenderness ratios (i.e. the heights/widths (Ω)) of the pipes (av. 0.6) show low to moderate correlation coefficients with vent parameters such as height (av. 258 m), area (av. 2.3 km²) and ellipticity (av. 1.5). The morpho-statistical analyses provided here show that ‘pipe’ formation mechanisms are mutually exclusive and that vent geometries are not particularly systematic in nature.